1. Field of the Invention
The present invention relates to mufflers for internal combustion engines in general, and, more particularly, to a high-performance muffler assembly including at least one valve assembly.
2. Description of the Prior Art
Typically, exhaust systems of internal combustion engines of all motor vehicles are equipped with a muffler for noise attenuation of the gases released from a combustion chamber of the internal combustion engines. Also, for internal combustion engines, especially diesel engines of large trucks, engine braking is an important feature for enhanced vehicle safety. For this reason, diesel engines in vehicles, particularly large trucks, are commonly equipped with an exhaust brake device for engine retarding. Exhaust brakes can be used on engines where compression release engine braking imparts too great of a load for the valve train. The exhaust brake device is characterized by increased sound level during engine braking operation.
The exhaust brake device consists of a restrictor element, such as a butterfly valve, mounted in the exhaust system upstream of a muffler. When this restrictor is closed, increasing exhaust backpressure resists the exit of gases during the exhaust cycle and provides a braking mode of operation. This system provides less braking power than a compression release engine brake, but also at less cost. With conventional fixed orifice exhaust brakes, the retarding power of an exhaust brake falls off sharply as engine speed decreases. This occurs because the restriction is typically optimized to generate maximum allowable backpressure at maximum engine speed. The optimized restriction is too large to be effective with the lower mass flow rates encountered at low engine speeds. In other words, the restriction is simply insufficient to be effective at the low engine speeds.
Typically, a range of engine operating speeds includes a low engine speed range (low engine speeds) and a high engine speed range (high engine speeds). Generally, the low engine speed range is defined as a speed range from an idle speed to a midrange speed, and high engine speed is defined as a speed range from the midrange speed to a maximum engine speed. In other words, the low engine speed is the engine speed at or near the lower end of the operating speed range of the engine, while the high engine speed is the engine speed at or near the upper end of the operating speed range of the engine.
While known exhaust systems of the internal combustion engines, including but not limited to those discussed above have proven to be acceptable for various vehicular applications, such devices are nevertheless susceptible to improvements that may enhance their performance.